From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_RED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 544A2C433E9 for ; Tue, 19 Jan 2021 15:21:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 190DB23138 for ; Tue, 19 Jan 2021 15:21:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387763AbhASPVb (ORCPT ); Tue, 19 Jan 2021 10:21:31 -0500 Received: from mail.kernel.org ([198.145.29.99]:50540 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389193AbhASPV1 (ORCPT ); Tue, 19 Jan 2021 10:21:27 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 01D6B23110; Tue, 19 Jan 2021 15:20:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1611069643; bh=yf0s5Hnc71ZDmBnzFPUIWJfODcCah0cMw3TOXpxitO8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=OPWVYTJT0MTCcxZuwblNq7+3b1gj+nFAHJTjvYu2HvxCc6I0hXTJ1f99Hx6kObw9S 3T2zTE+1KLE5UAjzDJOua6M3j09lPQu2AAaG1L6v07ro43OEJU5gr+mMkZZEm9L8xP K02wA0GlOA5PZ2VRAsLSociEkRhvBkyr0kwkafUk= Date: Tue, 19 Jan 2021 16:20:40 +0100 From: Greg Kroah-Hartman To: Daniel Vetter Cc: DRI Development , LKML , Stephen Rothwell , KVM list , Linux MM , Linux ARM , linux-samsung-soc , "open list:DMA BUFFER SHARING FRAMEWORK" , Bjorn Helgaas , Dan Williams , Daniel Vetter , Jason Gunthorpe , Kees Cook , Andrew Morton , John Hubbard , =?iso-8859-1?B?Suly9G1l?= Glisse , Jan Kara , Linux PCI Subject: Re: [PATCH v7 12/17] PCI: Revoke mappings like devmem Message-ID: References: <20201127164131.2244124-1-daniel.vetter@ffwll.ch> <20201127164131.2244124-13-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, Jan 19, 2021 at 03:34:47PM +0100, Daniel Vetter wrote: > On Tue, Jan 19, 2021 at 3:32 PM Greg Kroah-Hartman > wrote: > > > > On Tue, Jan 19, 2021 at 09:17:55AM +0100, Daniel Vetter wrote: > > > On Fri, Nov 27, 2020 at 5:42 PM Daniel Vetter wrote: > > > > > > > > Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims > > > > the region") /dev/kmem zaps ptes when the kernel requests exclusive > > > > acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is > > > > the default for all driver uses. > > > > > > > > Except there's two more ways to access PCI BARs: sysfs and proc mmap > > > > support. Let's plug that hole. > > > > > > > > For revoke_devmem() to work we need to link our vma into the same > > > > address_space, with consistent vma->vm_pgoff. ->pgoff is already > > > > adjusted, because that's how (io_)remap_pfn_range works, but for the > > > > mapping we need to adjust vma->vm_file->f_mapping. The cleanest way is > > > > to adjust this at at ->open time: > > > > > > > > - for sysfs this is easy, now that binary attributes support this. We > > > > just set bin_attr->mapping when mmap is supported > > > > - for procfs it's a bit more tricky, since procfs pci access has only > > > > one file per device, and access to a specific resources first needs > > > > to be set up with some ioctl calls. But mmap is only supported for > > > > the same resources as sysfs exposes with mmap support, and otherwise > > > > rejected, so we can set the mapping unconditionally at open time > > > > without harm. > > > > > > > > A special consideration is for arch_can_pci_mmap_io() - we need to > > > > make sure that the ->f_mapping doesn't alias between ioport and iomem > > > > space. There's only 2 ways in-tree to support mmap of ioports: generic > > > > pci mmap (ARCH_GENERIC_PCI_MMAP_RESOURCE), and sparc as the single > > > > architecture hand-rolling. Both approach support ioport mmap through a > > > > special pfn range and not through magic pte attributes. Aliasing is > > > > therefore not a problem. > > > > > > > > The only difference in access checks left is that sysfs PCI mmap does > > > > not check for CAP_RAWIO. I'm not really sure whether that should be > > > > added or not. > > > > > > > > Acked-by: Bjorn Helgaas > > > > Reviewed-by: Dan Williams > > > > Signed-off-by: Daniel Vetter > > > > Cc: Jason Gunthorpe > > > > Cc: Kees Cook > > > > Cc: Dan Williams > > > > Cc: Andrew Morton > > > > Cc: John Hubbard > > > > Cc: Jérôme Glisse > > > > Cc: Jan Kara > > > > Cc: Dan Williams > > > > Cc: Greg Kroah-Hartman > > > > Cc: linux-mm@kvack.org > > > > Cc: linux-arm-kernel@lists.infradead.org > > > > Cc: linux-samsung-soc@vger.kernel.org > > > > Cc: linux-media@vger.kernel.org > > > > Cc: Bjorn Helgaas > > > > Cc: linux-pci@vger.kernel.org > > > > Signed-off-by: Daniel Vetter > > > > -- > > > > v2: > > > > - Totally new approach: Adjust filp->f_mapping at open time. Note that > > > > this now works on all architectures, not just those support > > > > ARCH_GENERIC_PCI_MMAP_RESOURCE > > > > --- > > > > drivers/pci/pci-sysfs.c | 4 ++++ > > > > drivers/pci/proc.c | 1 + > > > > 2 files changed, 5 insertions(+) > > > > > > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > > > > index d15c881e2e7e..3f1c31bc0b7c 100644 > > > > --- a/drivers/pci/pci-sysfs.c > > > > +++ b/drivers/pci/pci-sysfs.c > > > > @@ -929,6 +929,7 @@ void pci_create_legacy_files(struct pci_bus *b) > > > > b->legacy_io->read = pci_read_legacy_io; > > > > b->legacy_io->write = pci_write_legacy_io; > > > > b->legacy_io->mmap = pci_mmap_legacy_io; > > > > + b->legacy_io->mapping = iomem_get_mapping(); > > > > pci_adjust_legacy_attr(b, pci_mmap_io); > > > > error = device_create_bin_file(&b->dev, b->legacy_io); > > > > if (error) > > > > @@ -941,6 +942,7 @@ void pci_create_legacy_files(struct pci_bus *b) > > > > b->legacy_mem->size = 1024*1024; > > > > b->legacy_mem->attr.mode = 0600; > > > > b->legacy_mem->mmap = pci_mmap_legacy_mem; > > > > + b->legacy_io->mapping = iomem_get_mapping(); > > > > > > Unlike the normal pci stuff below, the legacy files here go boom > > > because they're set up much earlier in the boot sequence. This only > > > affects HAVE_PCI_LEGACY architectures, which aren't that many. So what > > > should we do here now: > > > - drop the devmem revoke for these > > > - rework the init sequence somehow to set up these files a lot later > > > - redo the sysfs patch so that it doesn't take an address_space > > > pointer, but instead a callback to get at that (since at open time > > > everything is set up). Imo rather ugly > > > - ditch this part of the series (since there's not really any takers > > > for the latter parts it might just not make sense to push for this) > > > - something else? > > > > > > Bjorn, Greg, thoughts? > > > > What sysfs patch are you referring to here? > > Currently in linux-next: > > commit 74b30195395c406c787280a77ae55aed82dbbfc7 (HEAD -> > topic/iomem-mmap-vs-gup, drm/topic/iomem-mmap-vs-gup) > Author: Daniel Vetter > Date: Fri Nov 27 17:41:25 2020 +0100 > > sysfs: Support zapping of binary attr mmaps > > Or the patch right before this one in this submission here: > > https://lore.kernel.org/dri-devel/20201127164131.2244124-12-daniel.vetter@ffwll.ch/ Ah. Hm, a callback in the sysfs file logic seems really hairy, so I would prefer that not happen. If no one really needs this stuff, why not just drop it like you mention? thanks, greg k-h